Photovoltaic generators (PV=photovoltaics) generate electrical energy in response to light incidence. In order that the DC voltage generated by the photovoltaic generators can be fed into a public supply network, inverters are required. In the operational control of this inverter, a so-called “maximum power point (MPP) tracker” is used to continuously readjust the power drawn, such that a photovoltaic generator is operated, as much as possible, continuously at the point where maximum power is drawn “MPP” (maximum power point). For this purpose, the MPP tracker varies the current drawn or the voltage by a small magnitude, calculates in each case the product of current and voltage, and adjusts the current or voltage value in the direction of higher power. The sought optimum MPP point of the I-U characteristic curve forms the global maximum of the P-U characteristic curve.
In the case of partial shading of a photovoltaic generator, often more than one local maximum arises in the P-U characteristic curve. In this case, however, it is not possible for most MPP tracking methods to distinguish between local and global maxima. In practice, depending on the originating history of the shadow formation, this can lead to losses of yield if the MPP tracker proceeds to the local MPP and stays there.
In a search over the entire operating area of an installation, energetic losses can arise. Losses can be reduced by restricting searched areas.
ES 2 326 200 discloses a method for determining a maximum power point which permits to distinguish between local maxima and a global or absolute maximum. A search is performed taking account of one limiting condition for limiting the search area. A search under consideration of this condition is ended as soon as the determined power is bigger than the previous maximum power. The search is performed in a single direction in discrete steps having a width calculated from the previous maximum and the determined current.